How to loosen serpentine belt tension for alternator replacement?

[mattyh]

Hi all,

I need to replace the alternator on my Feb 1994 E280 sedan (Australian delivery). I'm no mechanic, but was hoping that this would be fairly straightforward after consulting youtube etc. My main problem is that the belt tensioner doesn't seem to correspond to the instructions I've found online. Apparently the M104 motor has an obvious 15mm nut that you can rotate clockwise to loosen tension (I can't find that nut). Alternatively the M103's have a vertical metal tube/nut near the power steering reservoir that can be twisted anti-clockwise to loosen tension but only after you loosen the mechanism by loosening the 19mm nut (I can see the adjustment tube/nut on my car but can't see the all-important 19mm nut!)

I'm hoping someone has instructions for my exact vintage E280. Nut head sizes would be great so I know I'm attacking the correct nut! I did a forum search here on "serpentine" and "tensioner" but this part of the puzzle seems to be skipped over (probably because it's so darn straightforward but sadly not for me! :-) )

Any help very much appreciated .... Matt

[crazycrowbar]

Where abouts in Australia are you located?
If you in the Bbne area I'll try to help you!

[John Green]

First trick is to remove the fan shroud so you have better access. You rotate the rear section to unlock it from the front, then remove the front and then the rear section, by lifting it upwards.

You then should be able to see what you are looking for.

[mattyh]

Thanks crazy crowbar ... you sound like a top bloke. Sadly I'm down in chilly Sydney.

And thanks also John. After a bit more googling it turns out some models have a 10mm hex to loosen the tensioner mechanism, and I've found that on mine (radiator plastic enclosure successfully removed). I'm not small but this hex nut just will not budge with the most force I can safely get onto a 10mm allen key! Unless there's some trick I'm missing (I have WD40 of course but no butane torch) I may have to call the professionals!

[mattyh]

Today's update is that the auto electrician visited yesterday and couldn't budge the 10mm hex with the standard gear he keeps in his van, either. So while I feel a bit better about not being able to move it myself, I'm a little concerned about what it's going to take to get the 10mm hex to budge ... hopefully it moves before it strips!

[Ivanerrol]

I've had to use a breaker bar at times just to get wiggle room.